Administrator's Reference Guide

Graphical target not workinh and GUI not working. Some times when we started server with GUI mode it will not work and only multi-user target will work in command prompt. To veryfy this use below command. # startx GUI will work till startx session persists. This menas legacy display login manager for the X Window System is not working properly and graphical login screen, shown shortly after boot up, log out, and when user-switching is also not working. This is due to gdm package has  replaced xorg-x11-xdm in RHEL 7. Verify "gdm" package status: Run below command: # rpm -Va &> /tmp/$(hostname)-$(date +"%Y-%m-%d-%H-%M-%S")-rpmva.txt Download the generated file in /tmp/ nad open in notepad++ editor. Search for "gdm". You can find that "missing  /run/gdm" How to Fix: 1- Reinstall the gdm package on your system: # yum reinstall gdm 2- Reboot the system in GUi mode and check the status If you still face the issue then, l...

Configure SNMP in Linux [RHEL7/RHEL8/CentOS] Packages for required for SNMP ------------------------------------------- net-snmp.x86_64                                                                                                    net-snmp-agent-libs.x86_64                                                                              net-snmp-libs.x86_64                                                      ...

Setting an Operating System Release During Registration # subscription-manager register --auto-attach --release=6.4 --username=admin@example.com... Setting an Operating System Release Preference: # subscription-manager release --list +-------------------------------------------+           Available Releases +-------------------------------------------+ 6.2 6.3 # subscription-manager release --set=6.3 Release version set to: 6.3 How to remove Installed Product version: # subscription-manager list +-------------------------------------------+     Installed Product Status +-------------------------------------------+ Product Name:   Red Hat Enterprise Linux Server Product ID:     69 Version:        7.7 Arch:           x86_64 Status:         Subscribed Status Details: Starts:         10/15/2018 Ends:...

Yum doesn't have enough cached data to continue # yum list all Loaded plugins: fastestmirror Loading mirror speeds from cached hostfile  One of the configured repositories failed (Unknown),  and yum doesn't have enough cached data to continue. At this point the only  safe thing yum can do is fail. There are a few ways to work "fix" this:      1. Contact the upstream for the repository and get them to fix the problem.      2. Reconfigure the baseurl/etc. for the repository, to point to a working         upstream. This is most often useful if you are using a newer         distribution release than is supported by the repository (and the         packages for the previous distribution release still work).      3. Run the command with the repository temporarily disabled             yum --disablerepo=<repoid> ...  ...

Reset  Postgress user  password in PostgreSQL Follow below steps to  Reset password for Postgress user in PostgreSQL: Also follow other topics: psql: could not connect to server: Permission denied How to install and initialize the PostgreSQL instance after installation Find the location of pg_hba.conf # find / -name pg_hba* /usr/local/pgsql/data/pg_hba.conf # vi /usr/local/pgsql/data/pg_hba.conf Add below parameter: local   all             all                                     trust Note: "trust" will allow all connection without prompting for password Login to Postgres: # psql -U postgres postgres=# Use below command to change password for postgress user: postgres=# alter user postgres with password 'NEW_PASSWORD'; Check for database: postgres=# \l         ...

psql: could not connect to server: Permission denied         Is the server running locally and accepting         connections on Unix domain socket "/tmp/.s.PGSQL.5432"? This is due to PostgreSQL service unable to create .s.PGSQL.5432 file in /tmp because of insufficient permission. You can also follow other topic: How to install and initialize the PostgreSQL instance after installation Reset Postgress user password in PostgreSQL Temporary Solution: # chmod -R 777 /tmp/ Once done psql command will start work, but after reboot it will stop working. # su - postgres $ psql psql (11.4) Type "help" for help. postgres=# Permanent Solution: # find / -name   postgresql.conf # vi /usr/local/pgsql/data/postgresql.conf Change permission for below parameter unix_socket_permissions = 0777 or comment below parameter in postgresql.conf # unix_socket_permissions = 0 # service postgres stop # service postgr...